LHC May Have Revealed First Hints of Higgs

Finally, physicists may have gotten a long-awaited prize with the latest data release from the Large Hadron Collider on Dec. 13, which show a possible signal for the elusive Higgs boson at around 125 gigaelectronvolts (GeV).

Two separate experiments confirm a small rise in the number of certain particle decay events occurring in a particular energy range. This could be a sign of the Higgs particle, which is a manifestation of the Higgs field required to give subatomic particles their mass.

The ATLAS experiment sees a signal consistent with a 126 GeV Higgs while the CMS collaboration reports an excess of events at 124 GeV. (A hydrogen atom is approximately 1 GeV, so if this were the Higgs particle it would be roughly equivalent to the mass of a cesium atom.) Even if this signal is not from the Higgs, both experiments narrowed down the range in which the Higgs particle could possibly show up, leaving only a small window between approximately 115 and 130 GeV.

“It’s getting very exciting. We are stepping into an interesting territory and we are starting to see some bumps there,” said physicist Greg Landsberg from Brown University in Providence, Rhode Island, who is a team member of the CMS group.

Even more exciting, a Higgs in this mass range would likely require new physics beyond the Standard Model — which describes the interactions of all known subatomic particles and forces –- in order to be stable. One possible extension, known as supersymmetry, posits the existence of a heavier partner to all known subatomic particles in order to solve certain problems with the Standard Model.

But physicists’ long wait for the Higgs may not quite be over.

As yet, the findings are “not very significant, and at best 50-50 (probably worse) that it is real,” wrote physicist Matt Strassler of Rutgers University, who was not involved with the work, in an e-mail. The observation is not much more than a “vague hint, and it is neither clear nor convincing.”

While both experiments see a similar signal, the observed particle decay events could have occurred by chance so this isn’t yet a discovery.

Next year, experiments will roughly quadruple the LHC dataset, giving an additional 15 percent boost in terms of the quality and power of the data, said Landsberg.

As mathematician Peter Woit of Columbia University wrote on his blog the day before the announcement, “One thing that can be predicted with certainty is a flood of papers from theorists claiming that their favorite model predicts this particular Higgs mass.”